DEBIAN-CVE-2026-92694: Debian/fastnetmon vulnerability

Published Nov 5, 2026

Updated

FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, FastNetMon's IPv6 top-talkers screen-draw thread in drawtableipv6() in src/fastnetmonlogic.cpp iterates ipv6hostcounters.averagespeedmap without holding countermapmutex while recalculatespeed() inserts new keys and may rehash the same map. The race requires networkslist to include the targeted IPv6 range. It causes confirmed undefined behavior under load; a process crash is plausible but was not observed, so reliable denial of service has not been established. No fixed release is available as of this review.

Affected Software

3 affected components

debian/fastnetmon*

Event History

Nov 5, 2026

CVE Published

via OSV·11:17 PM

Data Sourced

via OSV·11:17 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which deployments are exposed to this race condition?

Deployments using FastNetMon 1.2.9 or earlier are affected when the configured networks_list includes the targeted IPv6 range. The issue occurs in the IPv6 top-talkers screen-draw path while traffic processing adds new IPv6 counter entries.

What would an attacker need to do to trigger the issue?

The attacker would need to generate traffic involving an IPv6 address range included in networks_list, while the IPv6 top-talkers display thread is active. Concurrent insertion of new keys during screen drawing can cause the shared map to rehash without the required mutex.

Is this confirmed to be a reliable denial-of-service vulnerability?

No. Undefined behavior under load has been confirmed and a process crash is plausible, but a crash was not observed and reliable denial of service has not been established.

What can be done if no fixed release is available?

No fixed release is available as of the review. Limit networks_list to IPv6 ranges that must be monitored and avoid exposing the affected sensor to untrusted traffic for monitored IPv6 ranges where operationally feasible.

DEBIAN-CVE-2026-92694: Debian/fastnetmon vulnerability

Affected Software

Event History

Frequently Asked Questions

Which deployments are exposed to this race condition?

What would an attacker need to do to trigger the issue?

Is this confirmed to be a reliable denial-of-service vulnerability?

What can be done if no fixed release is available?

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Frequently Asked Questions

Which deployments are exposed to this race condition?

What would an attacker need to do to trigger the issue?

Is this confirmed to be a reliable denial-of-service vulnerability?

What can be done if no fixed release is available?